Is Python the favorite language of LLMs?

This a writeup of my talk at the Python Summit on October 19th, 2026. See the talk recording here. Do LLMs have preferences regarding programming languages? Why would they have any, and how would you notice it? Online, you might occasionally have come across the statement that LLMs are better with Python, or that they really prefer to use Python even when they shouldn't. Many of us are very skeptical about this: LLMs shouldn't have preferences regarding programming languages. Or do they? It turns out, this is a real research question, and some answers exist. In this post we will see what the research says about whether there is any preference from the LLM side regarding programming languages, what does that mean for your projects, and potentially for Python itself. Where might a bias like this be coming from? Was it just a thing of the past, or it's still a factor to keep in mind when starting a new project? What does “favorite” mean? I'm going to focus on two different…